RFC 2697 and RFC 2698 define a Single Rate Three Color Marker (srTCM) and Two Rate Three Color Marker (trTCM), respectively, which can be used as components in a Diffserv traffic conditioner [RFC2475, RFC2474].
A meter and a marker process each incoming packet stream. The Meter operates in one of two modes. In the Color-Blind mode, the Meter assumes that the packet stream is uncolored. In the Color-Aware mode the Meter assumes that some preceding entity has pre-colored the incoming packet stream so that each packet is either green, yellow, or red. The Marker (re)colors an IP packet according to the results of the Meter. The color is coded in the DS field (RFC 2474) of the packet in a PHB (Per-Hop Behavior) specific manner
RFC 2697 provides the standard for existing solutions of the srTCM and RFC 2698 provides the standard for existing solutions of the trTCM.